What Is Advanced Local Procedure Call (ALPC)? Definition

By NHI Mgmt Group Updated October 29, 2026 Domain: Architecture & Implementation

Advanced Local Procedure Call is a Windows inter-process communication mechanism for local client and server communication. It lets processes exchange messages through ports with security descriptors and impersonation support, so access control and process trust determine who can connect and what actions are allowed.

What ALPC Is Used For

Advanced Local Procedure Call, or ALPC, is Windows’ local inter-process communication mechanism for fast client-server messaging between processes on the same host. It is used when software components need structured, low-latency communication with explicit trust boundaries.

ALPC is more than a transport primitive. The security model around the port matters because access is mediated by security descriptors, and the server can inspect or act on the caller’s security context through impersonation.

How ALPC Security Boundaries Work

ALPC ports define which processes can connect and what level of interaction is allowed. That makes the mechanism useful for privileged Windows components, but it also means that misconfigured permissions can unintentionally widen access to a sensitive service interface.

Impersonation support is central to the trust model. A server may temporarily adopt the caller’s identity for authorization decisions, so the service must treat the caller context as security-sensitive data rather than as a simple message field.

Why ALPC Matters In Windows Architecture

ALPC is a core building block in Windows user-mode and system-component communication, especially where a service needs to broker requests from less-privileged processes. It is commonly paired with service isolation and access checks because the channel itself does not guarantee that the caller is trustworthy.

From an attacker’s perspective, ALPC is attractive because it can become a trusted path into higher-privilege software if the port ACL, message validation, or impersonation handling is weak. The mechanism is therefore part IPC design, part authorization design.

Common Failure Modes And Defensive Expectations

ALPC failures usually come from trust mistakes rather than from the protocol itself. The main issues are overly broad port permissions, insufficient caller validation, unsafe impersonation handling, and server code that assumes a connected client is automatically entitled to sensitive actions.

Defenders should think about ALPC as an interface that must be protected like any other privileged attack surface. A secure design keeps the port restricted, validates the caller’s context before performing privileged work, and limits the amount of authority transferred through impersonation.

Risk and Threat Considerations

ALPC can expose privileged Windows services to local abuse if the port security descriptor is too permissive or if the server trusts caller-controlled context too much. In a local attack chain, that can turn a messaging interface into an elevation or impersonation opportunity.

Failure mechanism: Weak access control, unsafe request parsing, or improper impersonation handling lets an untrusted local process reach code paths intended for a more trusted caller.

Impact: The result can include privilege escalation, service abuse, unauthorized actions inside a privileged process, or a broader post-compromise path within the host.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

MITRE ATT&CK addresses the attack and risk surface, while NIST SP 800-53 Rev 5 and CIS Controls v8 set the governance and control requirements practitioners need to meet.

Framework	Control / Reference	Relevance
MITRE ATT&CK	T1068 — Exploitation for Privilege Escalation	ALPC abuse can be part of local privilege escalation paths.
Recommendation — Map ALPC abuse to privilege-escalation techniques and hunt for local escalation attempts in telemetry.
NIST SP 800-53 Rev 5	AC-6 — Least Privilege	ALPC ports and impersonation should be restricted to the minimum required authority.
	IA-5 — Authenticator Management	ALPC trust depends on secure handling of identity-bearing context and related credentials.
	SC-7 — Boundary Protection	ALPC defines an internal trust boundary that must be controlled and monitored.
Recommendation — Apply AC-6 to restrict ALPC ports and service actions to least privilege. Protect identity material used in ALPC-mediated services and rotate exposed secrets promptly. Treat ALPC ports as protected internal boundaries and restrict access paths accordingly.
CIS Controls v8	CIS-6 — Access Control Management	ALPC access decisions depend on who can connect to the port and what they may do.
Recommendation — Restrict ALPC-accessible services to approved principals and remove unnecessary access.

Practitioner Guidance

Common misunderstanding: ALPC is sometimes treated as a low-level plumbing detail rather than a security boundary. In practice, the port configuration and caller context are part of the control plane, so they deserve the same review discipline as any exposed local service interface.

What to watch for: Review ALPC endpoints whenever a service runs with elevated rights, accepts structured requests from lower-privileged processes, or uses impersonation to make authorization decisions. The safest assumption is that every client message is potentially hostile until the server verifies it.

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NHIMG Editorial Note
Reviewed and updated by the NHIMG editorial team on October 29, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org

Advanced Local Procedure Call (ALPC)